#19 - Tanya would refrain from littering if everyone else

[Administrator]

Complete Question Explanation

Parallel Flaw—SN. The correct answer choice is (E)

The conditional reasoning here is clearly invalid, and can be diagrammed as follows:

Premise:

• If everyone refrains, then Tanya would refrain:
  
  Everyone refrain Tanya refrains

Flawed conclusion:

• Since her friends refrain, she must refrain:
  
  Her friends refrain Tanya refrains

As we can see, although the original sufficient condition (that everyone refrain) was not met, the author presumes that a different condition (that just her friends refrain) is sufficient to guarantee the same outcome.

The correct answer choice will likely reflect a similar case, wherein a sufficient condition is not met, but the author concludes that the necessary condition will take place anyway.

Answer choice (A): This flaw is different from that found in the stimulus. In this case, the invalid presumption is that because there are some goals in common, the people must share all of their goals.

Answer choice (B): The conditional reasoning presented here is clearly invalid, but this flawed reasoning is not the same as that found in the stimulus (that is, concluding the necessary condition in the absence of the sufficient condition), so this answer choice is incorrect.

Answer choice (C): The reasoning here appears valid and therefore cannot parallel the invalid reasoning found in the stimulus.

Answer choice (D): The flaw here is a classic Mistaken Reversal, much different from the flaw found in the stimulus, so this answer choice cannot be correct.

Answer choice (E): This is the correct answer choice, displaying the same type of invalid reasoning that we saw in the stimulus:

Premise:

• If all customers like the food, the restaurant must be exceptional:
  
  All customers like food exceptional restaurant

Flawed conclusion:

• Since those consulted like the food, it must be exceptional:
  
  Those consulted like the food exceptional restaurant

Exactly as we saw in the stimulus, this author presents a conditional statement, fails to meet the sufficient condition (all customers like the food), yet still concludes that the necessary condition will come to pass.

[jessicamorehead]

I chose the right answer with confidence. I noticed the stimulus made the flaw of equating "her friends (aka some people)" with "everyone else (aka all people)." I clearly saw this flaw represented in answer choice D, but I may have eliminated A for the wrong reasons. I didn't like its use of "some" and thought that the stimulus made a jump from "some" to "some," rather than "some" to "all." Can someone further explain why A is incorrect/if what I'm saying is even logical?

[Daniel Stern]

Hi Jessica:

Referring to Answer Choice A, you wrote:
"I didn't like its use of "some" and thought that the stimulus made a jump from "some" to "some," rather than "some" to "all." Can someone further explain why A is incorrect/if what I'm saying is even logical?"

In A, the move is from "residents share some goals" in the premise to "some residents" must share ALL goals in the conclusion. This is flawed, but not the same as the flaw in the stimulus that Tanya's friends can stand in for all people.

I hope that is helpful, good luck.
-- Dan

[basketball123]

Hello, I chose D. My reason was I felt it was the same flaw as it is equating all whales to all people, and blue whales to a small cohort of all whales just like how her friends are a small cohort of all people. Clearly this line of thinking was incorrect. Could you please advise?

[Adam Tyson]

Answer D has a slightly different flaw from the stimulus, basketball123. In the stimulus, we have a conditional relationship, which I'll put in completely abstract terms here:

If A, then B

Then, the author tells us that we have just some of A, and concludes that we must have B. That's the problem: we don't know if we actually have A, just a subset of it, so we cannot conclude B.

In answer D, we also have a conditional statement, which could be abstracted the same way. But then, instead of saying we have some of the sufficient condition (like, "blue whales need to surface for air"), they say that we have some of the necessary condition, and they use that to prove some of the sufficient condition. This is more like a Mistaken Reversal, which is not what happened in the stimulus. Just the fact that this answer is based on some of the necessary condition occurring, rather than a subset of the sufficient condition, takes this answer out of contention.

It was close, and I see what you liked about it, but it's a trap answer because of that switch between the sufficient and necessary conditions.